“Once a cheater, always a cheater.” The phrase is often leveled at serial cheaters, such as the beleaguered Tiger Woods. But is it true that all cheaters inevitably cheat again?

And what about the saying: “If he (or she) cheats with you, he’ll cheat on you.” We’ve seen this pattern played out in the tabloids often enough – a superstar falls for a leading lady or gentleman, leaves their spouse, marries the co-star, and then a few films down the line, repeats the pattern. But is this the exception or the rule?

These days we’re so inundated with stories of philandering celebs that it’s hard to distinguish between sensational tales of love, lust, and betrayal and information that reflects real-life probabilities. Fortunately for those who research these matters, there are plenty of ordinary cheaters willing to offer up histories of the kind of heartache that never hits the headlines. From these, researchers can extract somewhat more realistic statistics. Still, exact figures are hard to gather because one study often contradicts another. Therefore, with the proviso that these figures are not cast in stone, let’s look at some of the facts about cheating.

It is projected that 30 to 60% of all married individuals in the U.S. will engage in infidelity at some point during their marriage. This translates into nearly 80% of all American marriages impacted by cheating at some point. Approximately 2 to 3% of children are the product of infidelity.

Cheating appears to be most common among people under 30. In 2006, 19% of married men and 13% of married women under the age of 30 said they had been unfaithful. Contrast this with a 1991 survey showing that 13% of men and 11% of women of all ages had cheated. Clearly, cheating has grown far more pervasive over the years. It may also be that honesty of survey-takers has increased, too.

Some studies indicate that spouses who are unfaithful are most likely to start cheating 3 to 5 years into their marriage. Other research shows that cheating takes place within the first three years of marriage and within six months of the birth of a first child. While these two figures seem contradictory, one conclusion we could draw is that cheating typically begins at some point prior to the 5th year of marriage.

The actual likelihood of having an affair continues to increase with age and peaks when a man is 55 and a woman is 45 years old. Men are still 7 percent more likely to cheat than women. Upper-class women are 8 percent more likely to cheat than middle- and lower-class women, but men from all classes are equally likely to cheat.

Religious women are 4 percent less likely to have an affair than women who are not religious, but religion has no impact on whether men have affairs. People living in rural areas are less likely to cheat than people in cities – possibly because they feel less anonymous and more at risk of being caught.

Most studies conclude that levels of infidelity have increased significantly over the years, despite the fact that 90% of people claim to believe it is always wrong. Reasons include the proximity of women and men in the workplace and the availability of technology – including dating websites that specifically target married people seeking affairs – that has created both temptation and opportunity. In addition, relationships that begin as emotional affairs at work or online are more likely to progress to sexual affairs as time passes.

Assumptions that only people in unhappy marriages cheat are often incorrect. Although unhappy spouses are more likely to cheat, some affairs have little to do with the state of the marriage, or the quality of the sex in the marriage. Some people cheat for variety, or because they are tempted by a particular individual or – as one man told me – “just because we can.”

Famous people often cheat for the same reason that other powerful but less well-known individuals do: they crave attention and adulation from many. Such personalities are rarely satisfied with one partner because their need for novel experiences and multiple affirmations of desirability creates a demand for an ongoing supply of admirers. There is limited research about this type of cheater, however, and little information that distinguishes those who cheat just once from those who cheat again…or habitually.

Just as the figures about people who cheat vary among studies, so do stats on repeat cheating. One reference suggests that only about 22% of those who cheat do so again, while another finds that 55% repeat. According to an online survey of nearly 21,000 men and women who claimed to have had affairs, 60% of the men and half of the women were unfaithful more than once. Yet among the full group, only 38% of men and 50% of women said that they considered leaving their spouses, even though they felt that problems in the relationship (56% men, 65% women) or boredom with their sex life (44% men, 30% women) led to their infidelity.

While the above figures reflect patterns of cheating within a single marriage, less is known about those who have affairs in more than one long-term relationship. Which brings us to that common warning: “If he (or she) cheats with you, he’ll cheat on you.” Statistically speaking, this is less accurate than one might expect, for the simple reason that only a small percentage of cheaters wind up in long-term relationship with their mistresses or…hmm, what does one call the male equivalent? Paramours? Whatever the moniker, he is unlikely to be his married lover’s next husband. Usually, when a marriage breaks up, the affair soon winds down as well. Of course, this is not always true. We all know people who did leave a marriage for someone else. I can think of a man I knew some years ago who made a habit of marrying, then cheating, then divorcing and marrying the woman with whom he cheated, then cheating, then divorcing, and on and on – through 4 wives, last I heard. Clearly, in some instances common wisdom does bear fruit.

Among public figures, one can reel off names of the famous – Elizabeth Taylor and Albert Einstein for starters – who divorced spouses (or left long-term relationships) to marry their lovers and then cheated again. Take Einstein; he cheated on his first wife with his cousin, and later, while married to his cousin, carried on affairs with several other women. Although it’s unfair – not to mention unscientific – to generalize from such tales, it’s probably safe to say that someone who cheats in a first marriage will find cheating easier the next time around. Unless a person works hard to develop a different style of coping with marital discord or temptation, cheating can easily be a salve for any form of discontent.